Juror misconduct yesterday scuttled a death-penalty trial for a West Philadelphia man accused of killing two people and wounding a third in an attempted takeover of a crack-cocaine ring. Common Pleas Court Judge Steven R. Geroff declared a mistrial in the second day of jury deliberations after learning that several jurors had begun deliberating and commenting on evidence before the trial's end. "I think Judge Geroff did exactly what he should have done," said Edward D. Ohlbaum, a professor and director of trial advocacy at Temple University's Beasley School of Law. "This strikes me as pretty fundamental. . . . I would have been shocked had he done otherwise."